Continuous casting method of the slab

The present invention uses a flat roll, to reduce the center segregation and center porosity, a main object to provide a continuous casting method of the slab which satisfies the inhibition of surface cracks and internal cracks of the slab. The present invention, cross-section having a liquid core region therein a circular cast slab, by reduction by cylindrical horizontal roll, and forming a pair of plane parallel to the slab was completely solidified the slab, and roll pair of horizontal rolls of cylindrical, by reduction alternately between roll pairs of vertical rolls cylindrical, the slab, said set perpendicular set in a plane parallel to the parallel includes forming a surface, in the former step, the rolling reduction of the slab by each roll pair, and 3% or less than 0.5%, and the slab to the width of the contact portion between the slab and the roll the ratio of the width of unsolidified region in the transverse plane and from 0 to 7.15, the latter step, the rolling reduction of the slab by the horizontal rolls and vertical rolls, respectively 5.4% ～6.8%, cast a continuous casting method of the pieces.